Calibration of a Load Control Device for a Light-Emitting Diode Light Source

ABSTRACT

A load regulation device for controlling the amount of power delivered to an electrical load may be able to calibrate the magnitude of an output voltage of the load regulation device in order to control the magnitude of a load voltage across the electrical load to a predetermined level. The load regulation device may receive the feedback from a calibration device adapted to be coupled to load wiring near the electrical load. The feedback may indicate when the magnitude of the load voltage across the electrical load has reached a predetermined level. The load regulation device may gradually adjust the magnitude of the output voltage, receive the feedback from the calibration device, and then use the feedback to determine the magnitude of the output voltage corresponding to when the magnitude of the load voltage across the electrical load has reached the predetermined level.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/883,079, filed May 26, 2020; which is a continuation application ofU.S. patent application Ser. No. 15/959,593, filed on Apr. 23, 2018, nowU.S. Pat. No. 10,666,133, issued May 26, 2020, which is a divisionalapplication of U.S. patent application Ser. No. 14/975,560, filed Dec.18, 2015, now U.S. Pat. No. 9,954,435, issued Apr. 24, 2018, whichclaims the benefit of Provisional U.S. Patent Application No.62/094,128, filed Dec. 19, 2014, the disclosures of which areincorporated herein by reference in their entireties.

BACKGROUND

Light-emitting diode (LED) light sources (e.g., LED light engines) areoften used in place of or as replacements for conventional incandescent,fluorescent, or halogen lamps, and the like. LED light sources maycomprise a plurality of light-emitting diodes mounted on a singlestructure and/or provided in a suitable housing, for example. LED lightsources are typically more efficient and provide longer operationallives as compared to incandescent, fluorescent, and halogen lamps. Inorder to illuminate properly, an LED driver control device (i.e., an LEDdriver) may be coupled between an alternating-current (AC) source andthe LED light source for regulating the power supplied to the LED lightsource. The LED driver may regulate either the voltage provided to theLED light source to a particular value or the current supplied to theLED light source to a specific peak current value, or may regulate boththe current and voltage.

LED light sources may be rated to be driven via a number of differentcontrol techniques including, for example, a current load controltechnique or a voltage load control technique. An LED light source thatis rated for the current load control technique may be characterized bya rated current (e.g., approximately 350 milliamps) to which the peakmagnitude of the current through the LED light source should beregulated to ensure that the LED light source is illuminated to theappropriate intensity and color. In contrast, an LED light source thatis rated for the voltage load control technique may be characterized bya rated voltage (e.g., approximately 15 volts) to which the voltageacross the LED light source should be regulated to ensure properoperation of the LED light source. One or more parallel strings of LEDsin an LED light source rated for the voltage load control technique mayinclude a current balance regulation element to ensure that the parallelstrings have similar impedance so that similar current may be drawn ineach of the parallel strings.

LED drivers may be configured to dim the light output of an LED lightsource. Example methods of dimming LEDs include a pulse-width modulation(PWM) technique and a constant current reduction (CCR) technique.Pulse-width modulation dimming may be used for LED light sources thatare controlled in a current or voltage load control mode, for example.In pulse-width modulation dimming, a pulsed signal with a varying dutycycle is supplied to the LED light source. If an LED light source isbeing controlled using the current load control technique, the peakcurrent supplied to the LED light source is kept constant during an ontime of the duty cycle of the pulsed signal. However, as the duty cycleof the pulsed signal varies, the average current supplied to the LEDlight source may also vary, thereby varying the intensity of the lightoutput of the LED light source. If the LED light source is beingcontrolled using the voltage load control technique, the voltagesupplied to the LED light source is kept constant during the on time ofthe duty cycle of the pulsed signal in order to achieve the desiredtarget voltage level, and the duty cycle of the load voltage is variedin order to adjust the intensity of the light output. Constant currentreduction dimming may be used, for example, when an LED light source isbeing controlled using the current load control technique. In constantcurrent reduction dimming, current may be continuously provided to theLED light source while the DC magnitude of the current provided to theLED light source may be varied to thus adjust the intensity of the lightoutput. Examples of LED drivers are described in greater detail incommonly-assigned U.S. Pat. No. 8,492,988, issued Jul. 23, 2010,entitled CONFIGURABLE LOAD CONTROL DEVICE FOR LIGHT-EMITTING DIODE LIGHTSOURCE, and U.S. Patent Application Publication No. 2013/0063047,published Mar. 14, 2013, entitled LOAD CONTROL DEVICE FOR ALIGHT-EMITTING DIODE LIGHT SOURCE, the entire disclosures of which arehereby incorporated by reference.

If the LED light source is being controlled using the voltage loadcontrol technique, the magnitude of the voltage at the output of the LEDdriver may differ from the magnitude of the voltage across the LED lightsource due to, for example, the impedance of the electrical wiringbetween the LED driver and the LED light source. Accordingly, themagnitude of the voltage across the LED light source may not be equal tothe rated voltage of the LED light source. In addition, under theexample scenario described herein, the length of the electrical wiringbetween the LED driver and the LED light source may vary from oneinstallation and/or circuit to the next. As a result, the magnitude ofthe voltage across the LED light source and thus the intensity of theLED light source may vary from one installation and/or circuit to thenext for a given output voltage of the LED driver. If there are multipleinstallations of LED light sources controlled by a single LED driver ina room and each of LED light sources has a different length ofelectrical wiring between the LED driver and the respective LED lightsource, the intensities of all of the LED light sources may appeardifferent to an occupant of the room, which is undesirable.

SUMMARY

As described herein, a load regulation device for controlling the amountof power delivered to an electrical load may be able to calibrate themagnitude of an output voltage of the load regulation device in order tocontrol the magnitude of a load voltage across the electrical load to apredetermined level. The load regulation device may comprise a loadregulation circuit configured to generate the output voltage forproducing the load voltage across the electrical load, and a controlcircuit configured to adjust the magnitude of the output voltage of theload regulation circuit based on external feedback. The control circuitmay be configured to gradually adjust the magnitude of the outputvoltage and to receive the external feedback indicating when themagnitude of the load voltage across the electrical load has reached orexceeded the predetermined level. The load regulation device may use thefeedback to determine the magnitude of the output voltage correspondingto when the magnitude of the load voltage across the electrical load hasreached the predetermined level.

A load control system for controlling the amount of power delivered froma power source to an electrical load may comprise a load regulationdevice adapted to be coupled to the electrical load via load wiring, anda calibration device adapted to be coupled to the load wiring near theelectrical load. The load regulation device may be configured togenerate an output voltage for producing a load voltage across theelectrical load. The calibration device may be configured to providefeedback to the load regulation device indicating when the magnitude ofthe load voltage across the electrical load has reached a predeterminedlevel. The load regulation device may be configured to gradually adjustthe magnitude of the output voltage and to receive the feedbackindicating when the magnitude of the load voltage across the electricalload has reached the predetermined level from the calibration device.

A calibration circuit for calibrating an output voltage of a loadregulation device for an electrical load is also described herein. Thecalibration circuit may comprise a voltage sense circuit for sensing amagnitude of a load voltage developed across the electrical load, and acommunication circuit for providing feedback via the power wiring whenthe voltage sense circuit indicates that the magnitude of the loadvoltage has reached or exceeded a predetermined level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of an example load control systemfor controlling the amount of power delivered to an electric al load,such as, an LED light source.

FIG. 2A is a simplified signal diagram of a first example feedbackmechanism.

FIG. 2B is a simplified signal diagram of a second example feedbackmechanism.

FIG. 3 is a simplified block diagram of a load regulation device, suchas an LED driver, for controlling the intensity of an electrical load,such as an LED light source.

FIG. 4A is a first simplified block diagram of a calibration device thatmay be used to calibrate an output voltage of a load regulation device.

FIG. 4B is a second simplified block diagram of a calibration devicethat may be used to calibrate an output voltage of a load regulationdevice.

FIG. 4C is a third simplified block diagram of a calibration device thatmay be used to calibrate an output voltage of a load regulation device.

FIG. 5 is a first simplified flowchart of an example calibrationprocedure for calibrating a load voltage across an electrical load.

FIG. 6 is a second simplified flowchart of an example calibrationprocedure for calibrating a load voltage across an electrical load.

FIG. 7 is a simplified flowchart of an example feedback procedureexecuted while calibrating a load voltage across an electrical load.

FIG. 8 is a simplified block diagram of an example load control systemhaving a multiple-output load regulation device for controlling theamount of power delivered a plurality of electrical loads.

DETAILED DESCRIPTION

FIG. 1 is a simplified block diagram of an example load control system100 for controlling the amount of power delivered to an electrical load102, such as, a light-emitting diode (LED) light source (e.g., an LEDlight engine). The load control system 100 may comprise a loadregulation device 110, such as, an LED driver, for controlling theelectrical load 102 (e.g., controlling the intensity of a LED lightsource). The load regulation device 110 may be coupled to a powersource, e.g., an alternating-current (AC) power source 104 generating anAC line voltage. The electrical load 102 may be characterized by a ratedload voltage V_(RATED) (e.g., approximately 24 volts for a LED lightsource). The electrical load 102 is shown in FIG. 1 as two LEDsconnected in series but may comprise a single LED, a plurality of LEDsconnected in parallel or a suitable combination thereof, one or moreorganic light-emitting diodes (OLEDs), other lighting devices, amotorized window treatment, an HVAC system, and the like. Further, thepower source may comprise a direct-current (DC) power source generatinga DC supply voltage for certain electrical loads.

The load regulation device 110 may be configured to generate an outputvoltage V_(OUT), which may be coupled to the electrical load 102 viaload wiring 106. The electrical load 102 may develop a load voltageV_(LOAD) and conduct a load current I_(LOAD). Where the electrical load102 comprises an LED light source, the load regulation device 110 may beconfigured to turn the LED light source on and off, and to adjust theintensity of the LED light source between a minimum intensity (e.g.,approximately 1%) and a maximum intensity (e.g., approximately 100%).The load regulation device 110 may be configured to pulse-width modulatethe output voltage V_(OUT) to adjust the intensity of the LED lightsource between the minimum and maximum intensities, e.g., by adjustingthe duty cycle of the output voltage V_(OUT). In addition to or in lieuof pulse-width modulating the output voltage V_(OUT), the loadregulation device 110 may be configured to pulse-frequency modulate theoutput voltage V_(OUT) to adjust the intensity of the LED light sourcebetween the minimum and maximum intensities, e.g., by adjusting thefrequency of the output voltage V_(OUT)

The load regulation device 110 may be configured to receive wirelesssignals, e.g., radio-frequency (RF) signals 108, from one or more inputdevices. For example, where the electrical load 102 comprises a LEDlight source, the load regulation device 110 may be configured toreceive wireless signals from a wireless battery-powered light sensor120. The light sensor 120 may be configured to measure the total lightintensity at the sensor due to natural light (e.g., daylight orsunlight) and/or artificial light (e.g., as emitted by the LED lightsource). The light sensor 120 may be configured to transmit a digitalmessage including the measured light intensity to the load regulationdevice 110 via the RF signals 108. The load regulation device 110 may beconfigured to control the LED light source in response to the RF signalsreceived from the light sensor 120. Examples of wireless light sensorsare described in greater detail in commonly-assigned U.S. Pat. No.8,451,116, issued May 28, 2013, entitled WIRELESS BATTERY-POWEREDDAYLIGHT SENSOR, the entire disclosure of which is hereby incorporatedby reference.

The load control system 100 may comprise other types of input devices,such as, for example, occupancy sensors, vacancy sensors, motionsensors, security sensors, proximity sensors, daylight sensors, windowsensors, shadow sensors, cloudy-day sensors, temperature sensors,humidity sensors, radiometers, pressure sensors, smoke detectors, carbonmonoxide detectors, air-quality sensors, fixture sensors, partitionsensors, keypads, battery-powered remote controls, kinetic orsolar-powered remote controls, key fobs, mobile communication devices(such as cell phones, smart phones, tablets), personal digitalassistants, personal computers, laptops, timeclocks, audio-visualcontrols, safety devices, power monitoring devices (such as powermeters, energy meters, utility submeters, utility rate meters), centralcontrol transmitters, residential, commercial, or industrialcontrollers, or any combination of these input devices. Examples of loadcontrol systems are described in greater detail in commonly-assignedU.S. Patent Application Publication No. 20140001977, published Jan. 2,2014, entitled LOAD CONTROL SYSTEM HAVING INDEPENDENTLY-CONTROLLED UNITSRESPONSIVE TO A BROADCAST CONTROLLER, and U.S. patent application Ser.No. 13/830,237, filed Mar. 14, 2013, entitled COMMISSIONING LOAD CONTROLSYSTEMS, the entire disclosures of which are hereby incorporated byreference.

The magnitude of the load voltage V_(LOAD) at the electrical load 102may differ from the magnitude of the output voltage V_(OUT) at the loadregulation device 110. The voltage difference may be caused by one ormore conditions including, for example, the impedance (e.g., resistance)of the load wiring 106 and the magnitude of the load current I_(LOAD).Since the length of the load wiring 106 may vary from one installationand/or circuit to the next, the magnitude of the load voltage V_(LOAD)at the electrical load 102 and thus certain functional aspects of theelectrical load 102 (e.g., the intensity of an LED light source) mayvary from one installation and/or circuit to the next at a givenmagnitude of the output voltage V_(OUT). The load regulation device 110may be configured to calibrate the magnitude of the output voltageV_(OUT), such that the magnitude of the load voltage V_(LOAD) isapproximately equal to the rated load voltage V_(RATED) of theelectrical load 102 independent of the length of the load wiring 106between the load regulation device 110 and the electrical load 102. Thecalibration may be automatic (e.g., during power-up of the loadregulation device 110) or in response to an actuation event (e.g., theactuation of a button or reception of a digital message). The loadregulation device 110 may be configured to gradually adjust (e.g., stepup) the magnitude of the output voltage V_(OUT) and subsequently receiveexternal feedback that the magnitude of the load voltage V_(LOAD) hasreached or exceeded a predetermined level (e.g., the rated load voltageV_(RATED) or a predetermined voltage V_(PREDETERMINED) that is slightlybelow the rated voltage). In an example, the feedback may be provided bya device located near the electrical load 102 and capable of obtaining afairly accurate reading of the load voltage V_(LOAD) of the electricalload 102. In another example, the feedback may be provided by a deviceor circuit located inside the electrical load 102 and configured tomeasure the load voltage V_(LOAD). The load regulation device 110 may beconfigured to use the feedback to determine the appropriate magnitude towhich to control the output voltage V_(OUT) so that the magnitude of theload voltage V_(LOAD) may be approximately equal to the predeterminedlevel (e.g., the rated load voltage V_(RATED) of the electrical load 102or a predetermined voltage V_(PREDETERMINED)) during normal operation.

The load regulation device 110 may be configured to measure themagnitudes of the output voltage V_(OUT) and the load current I_(LOAD)to determine a relationship between the output voltage V_(OUT) and loadcurrent I_(LOAD). For example, the load regulation device 110 may beconfigured to determine an I-V (current-voltage) curve of the outputvoltage V_(OUT) and the load current I_(LOAD) (e.g., a plot of thecurrent versus voltage at the output of the load regulation device 110).The load regulation device 110 may use the I-V curve to determine themagnitude of output voltage V_(OUT) at which the magnitude of the loadvoltage V_(LOAD) is approximately equal to the predetermined level(e.g., the rated load voltage V_(RATED) or a predetermined voltage levelV_(PREDETERMINED)). The I-V curve or more broadly, the relationshipbetween the output voltage V_(OUT) and load current I_(LOAD) may besaved to a storage device (e.g., a database device) so that similardetermination may be made automatically during a subsequent power-up ofthe load regulation device 110.

The load control system 100 may comprise a calibration device 130 (e.g.,a calibration circuit) coupled to (e.g., in parallel with) theelectrical load 102 near (e.g., immediately adjacent to) the electricalload 102. The exact distance between the calibration device and theelectrical load 202 may vary from one installation to the next, but itis contemplated that the calibration device 130 should be placed at alocation that enables the calibration device 130 to fairly accuratelymeasure and/or control one or more operating parameters of theelectrical load 102 (e.g., without significant impact from the loadwiring). For example, one or more components of the calibration device130 may be configured to be connected in parallel with the electricalload 102 and to sense the magnitude of the load voltage V_(LOAD) acrossthe electrical load 102. For example, the calibration device 130 may beinstalled at a location that is within the final 5% of the load wiringleading to the electrical load 102.

In some examples, the calibration device 130 may be located at (e.g.,being a part of) the electrical load 102. For instance, the electricalload 102 may comprise an enclosure and the calibration device 130 (e.g.,a calibration circuit) may be installed inside the enclosure to measureand/or control one or more operating parameters of the electrical load102.

The calibration device 130 may be configured to provide feedback to theload regulation device 110 in response to sensing the magnitude of theload voltage V_(LOAD). The load regulation device 110 may be configuredto adjust the magnitude of the output voltage V_(OUT) based on thefeedback such that the load voltage V_(LOAD) is substantially equal toor slightly less than the rated load voltage V_(RATED). For example, thecalibration device 130 may be configured to provide the feedback to theload regulation device 110 when the magnitude of the load voltageV_(LOAD) has exceeded the predetermined level. The predetermined levelV_(PREDETERMINED) may be the rated load voltage V_(RATED) (e.g., asshown in FIG. 2A) or a voltage level that is slightly below (e.g., byapproximately 0.2 volt) the rated load voltage V_(RATED) (e.g., as shownin FIG. 2B). The load regulation device 110 may be configured togradually increase (e.g., step up) the magnitude of the output voltageV_(OUT) until receiving the feedback from the calibration device 130that the load voltage has exceeded the predetermined voltageV_(PREDETERMINED). In some examples (e.g., when the predeterminedvoltage V_(PREDETERMINED) is set to be equal to the rated load voltageV_(RATED), as shown in FIG. 2A), after receiving the feedback that theload voltage has exceeded the predetermined level, the load regulationdevice 110 may be configured to slightly decrease (e.g., step down) themagnitude of the output voltage V_(OUT) (e.g., by approximately 0.2volt) to a final value (e.g., a normal operating output voltage) suchthat the magnitude of the load voltage V_(LOAD) no longer exceeds thepredetermined/rated level. In some examples (e.g., when thepredetermined level V_(PREDETERMINED) is set to be slightly below therated load voltage V_(RATED), as shown in FIG. 2B), after receiving thefeedback that the load voltage has exceeded the predetermined levelV_(PREDETERMINED), the load regulation device 110 may be configured tomaintain (e.g., without stepping down) the current magnitude of theoutput voltage V_(OUT) as the final value (e.g., a value at which themagnitude of the load voltage V_(LOAD) may be slightly above thepredetermined level V_(PREDETERMINED), but may still be below the ratedload voltage V_(RATED), as shown in FIG. 2B). The load regulation device110 may comprise a memory and may be configured to store the final valueof the output voltage V_(OUT) in the memory for use during normaloperation.

The calibration device 130 may be configured to provide the feedback tothe load regulation device 110 via the load wiring 106. For example, asillustrated in FIG. 2A, the predetermined level V_(PREDETERMINED) may beset to be equal to the rate voltage V_(RATED). The calibration device130 may be configured to generate a current spike (e.g., a currentpulse) on the load wiring 106 when the load voltage has exceeded thepredetermined level V_(PREDETERMINED). The load regulation device 110may be configured to gradually increase (e.g., through a plurality ofperiodic step) the magnitude of the output voltage V_(OUT) untilreceiving the current spike. The load regulation device 110 may befurther configured to decrease (e.g., step down) the output voltageV_(OUT) slightly after receiving the current spike such that themagnitude of the load voltage V_(LOAD) no longer exceeds thepredetermined level V_(PREDETERMINED) (or the rated voltage V_(RATED)).By way of another example, as illustrated in FIG. 2B, the predeterminedlevel V_(PREDETERMINED) may be set to be slightly below (e.g., byapproximately 0.2 volt) the rate voltage V_(RATED). The calibrationdevice 130 may be configured to generate periodic (e.g., at regularintervals) current spikes on the load wiring when the magnitude of theload voltage V_(LOAD) has not reached the predetermined levelV_(PREDETERMINED), and to stop generating the current spikes when themagnitude of the load voltage V_(LOAD) has reached or exceeded thepredetermined level V_(PREDETERMINED). The load regulation device 110may be configured to gradually increase (e.g., step up) the magnitude ofthe output voltage V_(OUT) and to sense the current spikes indicatingthat the magnitude of the load voltage V_(LOAD) has not reached thepredetermined level V_(PREDETERMINED). The load regulation device 110may be further configured to maintain the magnitude of the outputvoltage V_(OUT) after not sensing any current spike for a period longerthan the regular interval. At the maintained output voltage level, theload voltage V_(LOAD) may be equal to or slightly above thepredetermined level V_(PREDETERMINED), but may still be below the ratedvoltage V_(RATED).

The magnitude of each gradual adjustment to the output voltage V_(OUT)(e.g., the step size of the plurality of period steps shown in FIGS. 2Aand 2B) may be determined based on one or more factors including, forexample, the desired duration of the calibration process and/or finetuning capabilities. For instance, where quick calibration is desirable,the magnitude (e.g., step size) of each adjustment may be set to alarger value; where fine turning is more important, the magnitude ofeach adjustment may be set to a smaller value. In an examples, a stepsize of approximately 0.2 volt may be used. In other examples, adifferent step size may be more suitable.

In addition to or in lieu of providing the feedback via one or morecurrent spikes, the calibration device 130 may be configured to providethe feedback to the load regulation device 110 by wirelesslytransmitting a digital message via the RF signal 108 or by transmittinga digital message on the load wiring 106 using, for example, apower-line communication (PLC) technology. Further, the calibrationdevice 130 may be configured to provide the feedback to the loadregulation device 110 by transmitting a digital message via anotherwired or wireless communication medium, such as, for example, infraredor optical communications. For example, the load regulation device 110and the calibration device 130 may be configured to transmit and receivewireless signals according to a proprietary protocol (such as the LutronClearConnect protocol), or a standard protocol (such as one of WIFI,ZIGBEE, Z-WAVE, KNX-RF, ENOCEAN RADIO protocols, and the like). Forexample, the load regulation device 110 and the calibration device 130may be configured to transmit and receive wireless signals usingdifferent wireless technologies, such as Bluetooth and/or near fieldcommunication (NFC) technologies.

In addition, the load regulation device 110 may be configured to receivethe feedback via a wireless signal received from one of the inputdevices described herein. For example, where the electrical load 102comprises an LED light source, the load regulation device 110 may beconfigured to determine that the light emitted by the LED light sourcemay have reached or exceeded a predetermined level in response to adigital message received from the light sensor 120 via the RF signals108. By way of another example, the load regulation device 110 may beconfigured to determine that the load voltage has reached or exceeded apredetermined level in response to a digital message received from amobile communication device (e.g., a smart phone or a tablet). By way ofyet another example, the load regulation system 100 may comprise asystem controller that is configured to communicate (e.g., via a wiredor wireless communication circuit) with both the calibration device 130and the load regulation device 110. The calibration device 130 may beconfigured to communicate with (e.g., provide the feedback to) thesystem controller. The system control may then control the loadregulation device 110 based on the communication with the calibrationdevice 130.

In addition to or in lieu of providing an indication of whether the loadvoltage has reached or exceeded the predetermined level, the feedbackdescribed herein (e.g., a digital message) may include informationregarding the actual magnitude of the load voltage and/or thediscrepancy between the actual load voltage and the predetermined level.The load regulation device 110 may be configured to interpret theinformation included in the feedback and to adjust the output voltageV_(OUT) based on the information so that the load voltage may beapproximately equal to the predetermined level.

The load regulation device 110 and/or the calibration device 130 may beconfigured to initialize the calibration procedure. For example, thecalibration procedure may be executed every time that the loadregulation device 110 is powered up, or only the first (e.g., initial)time that the load regulation device 110 is powered up. The calibrationprocedure may be started by power cycling the load regulation device 110and/or the calibration device 130 a number of times within apredetermined period of time, for example. The calibration procedure maybe executed in response to the actuation of a button on the loadregulation device 110 and/or the calibration device 130. The calibrationprocedure may be executed in response to a digital message received, forexample, via the RF signals 108 or via another communication medium. Thecalibration procedure may be executed in response to any step change inthe magnitude of the load current I_(LOAD). Other ways to trigger thecalibration procedure are also within the scope of this disclosure.

The load control system 100 may comprise one or more other types of loadcontrol devices, such as, for example, a dimming circuit for a lightingload, such as incandescent lamp or halogen lamp; an electronic dimmingballast for a fluorescent lamp; a screw-in luminaire including a dimmercircuit and an incandescent or halogen lamp; a screw-in luminaireincluding a ballast and a compact fluorescent lamp; a screw-in luminaireincluding an LED driver and an LED light source; an electronic switch,controllable circuit breaker, or other switching device for turning anappliance on and off; a plug-in load control device, controllableelectrical receptacle, or controllable power strip for controlling oneor more plug-in loads; a motor control unit for controlling a motorload, such as a ceiling fan or an exhaust fan; a drive unit forcontrolling a motorized window treatment or a projection screen;motorized interior or exterior shutters; a thermostat for a heatingand/or cooling system; a temperature control device for controlling asetpoint temperature of an HVAC system; an air conditioner; acompressor; an electric baseboard heater controller; a controllabledamper; a variable air volume controller; a fresh air intake controller;a ventilation controller; a hydraulic valves for use radiators andradiant heating system; a humidity control unit; a humidifier; adehumidifier; a water heater; a boiler controller; a pool pump; arefrigerator; a freezer; a television or computer monitor; a videocamera; an audio system or amplifier; an elevator; a power supply; agenerator; an electric charger, such as an electric vehicle charger; andan alternative energy controller.

FIG. 3 is a simplified block diagram of a load regulation device 200(e.g., an LED driver), which may be deployed as the load regulationdevice 110 in the load control system 100 shown in FIG. 1. The loadregulation device 200 may be configured to control the amount of powerdelivered to an electrical load 202, such as, an LED light source, andto thus control certain functional aspects of the electrical load 202,such as, the intensity of the LED light source. The load regulationdevice 200 may comprise a hot terminal H and a neutral terminal that areadapted to be coupled to an alternating-current (AC) power source (e.g.,the AC power source 104).

The load regulation device 200 may comprise a load regulation circuit210, which may control the amount of power delivered to the electricalload 202. For example, where the electrical load 202 comprises an LEDlight source, the load regulation circuit 210 may control the intensityof the LED light source between a low-end (i.e., minimum) intensityL_(LE) (e.g., approximately 1-5%) and a high-end (i.e., maximum)intensity L_(HE) (e.g., approximately 100%) by pulse-width modulating orpulse-frequency modulating the output voltage V_(OUT). The loadregulation circuit 210 may comprise, for example, a forward converter, aboost converter, a buck converter, a flyback converter, a linearregulator, or any suitable LED drive circuit for adjusting the intensityof the LED light source. Examples of load regulation circuits for LEDdrivers are described in greater detail in commonly-assigned U.S. Pat.No. 8,492,987, issued Jul. 23, 2010, and U.S. Patent ApplicationPublication No. 2014/0009085, filed Jan. 9, 2014, both entitled LOADCONTROL DEVICE FOR A LIGHT-EMITTING DIODE LIGHT SOURCE, the entiredisclosures of which are hereby incorporated by reference.

The load regulation device 200 may comprise a control circuit 220, e.g.,a controller, for controlling the operation of the load regulationcircuit 210. The control circuit 220 may comprise, for example, adigital controller or any other suitable processing device, such as, forexample, a microcontroller, a programmable logic device (PLD), amicroprocessor, an application specific integrated circuit (ASIC), or afield-programmable gate array (FPGA).

The control circuit 220 may generate a drive control signal V_(DRIVE)that is provided to the load regulation circuit 210 for adjusting themagnitude of an output voltage V_(OUT) (to thus adjust the magnitude ofa load voltage V_(LOAD) generated across the electrical load 202) and/orthe magnitude of a load current I_(LOAD) conducted through theelectrical load 202 (to thus control the intensity of an LED lightsource to a target intensity L_(TRGT), for example). The load regulationdevice 200 may further comprise a voltage sense circuit 222 (which maybe configured to generate an output voltage feedback signal V_(FB-VOLT)that may indicate the magnitude of the output voltage V_(OUT)) and acurrent sense circuit 224 (which may be configured to generate a loadcurrent feedback signal V_(FB-CRNT) that may indicate the magnitude ofthe load current I_(LOAD)). The control circuit 220 may receive thevoltage feedback signal V_(FB-VOLT) and the load current feedback signalV_(FB-CRNT), and control the drive control signal V_(DRIVE) to adjustthe magnitude of the output voltage V_(OUT) and/or the magnitude of theload current I_(LOAD) (e.g., to thus control the intensity of the LEDlight source to the target intensity L_(TRGT)) using a control loop.

The control circuit 220 may be coupled to a storage device (e.g., amemory 226) for storing the operational characteristics of the loadregulation device 200 (e.g., the target intensity L_(TRGT), the low-endintensity L_(LE), the high-end intensity L_(HE), etc., of an LED lightsource). The load regulation device 200 may further comprise a powersupply 228, which may generate a direct-current (DC) supply voltageV_(CC) for powering the circuitry of the load regulation device 200.

The load regulation device 200 may also comprise a first communicationcircuit 230, which may be coupled to, for example, a wired communicationlink or a wireless communication link, such as a radio-frequency (RF)communication link or an infrared (IR) communication link. The controlcircuit 220 may be configured to update the operational characteristics(e.g., the target intensity L_(TRGT) of an LED light source) stored inthe memory 226 in response to digital messages received via the firstcommunication circuit 230. In addition to or in lieu of receivingdigital messages via the first communication circuit 230, the loadregulation device 200 may be configured to receive a signal (e.g., aphase-control signal) from one of the input devices described herein(e.g., a dimmer switch) for determining the operational characteristicsof the electrical load 202 (e.g., the target intensity L_(TRGT) for theLED light source).

The control circuit 220 may be configured to automatically calibrate themagnitude of the output voltage V_(OUT), such that the magnitude of theload voltage V_(LOAD) across the electrical load 202 is approximatelyequal to the rated load voltage V_(RATED) of the electrical load 202.For example, during a calibration mode, the control circuit 220 may beconfigured to periodically increase the magnitude of the output voltageV_(OUT) by a voltage step A_(OUT) and subsequently receive feedback thatthe load voltage V_(LOAD) has reached or exceeded a predetermined level(e.g., has reached and/or exceeded the rated load voltage V_(RATED) ofthe electrical load 202). In other words, the control circuit 220 may beconfigured to gradually increase (e.g., through a plurality of periodicsteps) the magnitude of the output voltage V_(OUT) until the controlcircuit 220 receives the feedback that the magnitude of the load voltageV_(LOAD) has reached or exceeded the predetermined level. The controlcircuit 220 may decrease the magnitude of the output voltage V_(OUT) bya certain amount (e.g., the voltage step A_(OUT)) after receiving thefeedback such that the output voltage V_(OUT) may reach a finalmagnitude at which the load voltage V_(LOAD) no longer exceeds thepredetermined level. The final magnitude of the output voltage V_(OUT)may be stored in the memory 226 and used by the control circuit tocontrol the magnitude of the output voltage V_(OUT) to the storedmagnitude during normal operation.

By way of another example, during the calibration mode, the controlcircuit 220 may be configured to increase (e.g., step up by a voltagestep A_(OUT)) the magnitude of the output voltage V_(OUT) and to senseregular-interval feedback that the load voltage V_(LOAD) has not reachedthe predetermined level (e.g., has not reached or exceeded the ratedload voltage V_(RATED) of the electrical load 202). Subsequently, whenno feedback is received for a period longer than the regular interval,the control circuit 220 may be configured to decrease the magnitude ofthe output voltage V_(OUT) by a certain amount (e.g., the voltage stepA_(OUT)) or to maintain magnitude of the output voltage V_(OUT). Thefinal magnitude of the output voltage may be stored in memory 226. Thecontrol circuit 220 may be configured to control the magnitude of theoutput voltage V_(OUT) to the stored final magnitude during normaloperation.

The control circuit 220 may be configured to gradually adjust themagnitude of the output voltage V_(OUT), measure the magnitude of theoutput voltage V_(OUT) (e.g., via the voltage sense circuit 222) and/orthe magnitude of the load current I_(LOAD) (e.g., via the current sensecircuit 224), and store these values in the memory 226. The controlcircuit 220 may then be configured to determine a relationship betweenthe output voltage V_(OUT) and the load current I_(LOAD) (e.g., an I-Vcurve of the output voltage and the load current). The control circuit210 may be configured to use the relationship between the output voltageV_(OUT) and the load current I_(LOAD) to determine the magnitude ofoutput voltage V_(OUT) at which the magnitude of the load voltageV_(LOAD) is approximately equal to the rated load voltage V_(RATED), andmay store that magnitude in the memory 226.

The control circuit 220 may also be configured to receive the feedbackthat the load voltage has reached or exceeded the predetermined level inone or more digital messages received via the first communicationcircuit 230. For example, the control circuit 210 may be configured toreceive a digital message from a calibration device (e.g., thecalibration device 130 shown in FIG. 1) indicating that the magnitude ofthe load voltage V_(LOAD) has reached the predetermined level. Thecalibration device may be coupled to the electrical load 202 (e.g., oneor more components of the calibration device may be connected inparallel with the electrical load 202) near (e.g., immediatelyadjacently to) the electrical load 202. The exact distance between thecalibration device and the electrical load 202 may vary from oneinstallation to the next, but it is contemplated that the calibrationdevice 130 should be placed at a location that enables the calibrationdevice to fairly accurately measure and/or control one or more operatingparameters of the electrical load 202 (e.g., without significant impactfrom the load wiring). In some examples, the calibration device may belocated at (e.g., being a part of) the electrical load 202. Forinstance, the electrical load 202 may comprise an enclosure and thecalibration device (e.g., a calibration circuit) may be installed insidethe enclosure to measure and/or control one or more operating parametersof the electrical load 202. Further, where the electrical load 202comprises an LED light source, the control circuit 220 may be configuredto receive a digital message indicating that the light emitted by theLED light source may have reached or exceeded a predetermined level froma light sensor (e.g., the light sensor 120 shown in FIG. 1).

In addition to or in lieu of providing an indication of whether the loadvoltage has reached the predetermined level, the feedback (e.g., one ormore digital messages) described herein may include informationregarding the actual magnitude of the load voltage and/or thediscrepancy between the load voltage and the predetermined level. Thecontrol circuit 220 (e.g., a microprocessor) may be configured tointerpret the information included in the feedback and to adjust theoutput voltage V_(OUT) based on the information so that the load voltagemay be approximately equal to the predetermined level.

The load regulation device 200 may further comprise a secondcommunication circuit 232 coupled to the load wiring to the electricalload 202 (e.g., the load wiring 106 shown in FIG. 1). The secondcommunication circuit may be configured to receive feedback from acalibration device coupled to (e.g., in parallel with) the electricalload (e.g., the calibration device 130) via the load wiring. Forexample, the second communication circuit 232 may be configured toreceive a digital message from the calibration device via the loadwiring, e.g., a power-line communication (PLC) signal. In addition to orin lieu of receiving the digital message, the second communicationcircuit 232 may be configured to receive one or more current spikes(e.g., current pulses) indicating whether the magnitude of the loadvoltage V_(LOAD) has reached or exceeded the predetermined level. In oneor more examples, the load regulation device 200 may not comprise thesecond communication circuit 232, and the control circuit 210 may beconfigured to receive the current spikes from the calibration device viathe voltage sense circuit 222 and/or the current sense circuit 224.

FIGS. 4A-4C are simplified block diagrams of example calibration devices(e.g., calibration circuits) 300, 320, 340, which may be deployed as thecalibration device 130 in the load control system 100 shown in FIG. 1.The calibration devices 300, 320, 340 may each be configured to becoupled to (e.g., in parallel with) an electrical load (e.g., the LEDlight source described herein) near the electrical load. The calibrationdevices 300, 320, 340 may comprise electrical terminals 302, 322, 342(e.g., screw terminals, flying leads, etc.), respectively, that areconfigured to be coupled to load wiring between the electrical load anda load regulation device (e.g., the load wiring 106). The calibrationdevices 300, 320, 340 may comprise voltage sense circuits 304, 324, 344,respectively. The voltage sense circuits 304, 324, 344 may be coupledbetween their corresponding terminals (e.g., terminals 302, 322, 342)and be responsive to the magnitude of the load voltage V_(LOAD) at theelectrical load. One or more of the calibration devices 300, 320, 340may also comprise a communication circuit (e.g., the communicationcircuit 306, 326, or 346) for providing feedback concerning whether theload voltage V_(LOAD) has reached or exceeded a predetermined level, theactual magnitude of the load voltage V_(LOAD), and/or the discrepancybetween the magnitude of the load voltage V_(LOAD) and the predeterminedlevel.

The voltage sense circuits 304, 324, 344, and the communication circuits306, 326, 346 may comprise analog and/or digital circuits. For example,the voltage sense circuit 324 may comprise a shunt regulator and thecommunication circuit 326 may comprise a current sink circuit (e.g.,including a field-effect transistor (FET) as shown in FIG. 4B)configured to conduct one or more pulses of current through the loadwiring based on indications provided by the shunt regulator concerningwhether the magnitude of the load voltage V_(LOAD) has exceeded thepredetermined level. By way of another example, one or more of thevoltage sense circuits 304, 324, 344 may comprise a voltage dividercoupled between the corresponding terminals for generating a scaledvoltage that is proportional to the magnitude of the load voltageV_(LOAD) and a digital controller configured to sense the scaledvoltage. The digital controller may be further configured to determinethe magnitude of the load voltage V_(LOAD) and/or whether the magnitudeof the load voltage V_(LOAD) has reached or exceeded the predeterminedlevel. For example, the digital controller may be configured to samplethe scaled voltage using an analog-to-digital converter (ADC), derivethe magnitude of the load voltage V_(LOAD) based on the scaled voltage,and/or determine whether the magnitude of the load voltage V_(LOAD) hasreached or exceeded the predetermined level. The communication circuitsdescribed herein may comprise a digital communication circuit fortransmitting a digital message via a wired or wireless communicationlink in response to the digital controller of the voltage sense circuitdetermining the magnitude of the load voltage V_(LOAD) and/or whetherthe magnitude of the load voltage V_(LOAD) has exceeded thepredetermined level. For example, the digital message may comprise datafields representing the magnitude of the load voltage V_(LOAD), thediscrepancy between the magnitude of the load voltage V_(LOAD) and thepredetermined level, and/or an indication of whether the magnitude ofthe load voltage V_(LOAD) has reached or exceeded the predeterminedlevel. Either or both of the digital controller and the communicationcircuit may comprise, for example, a digital processing device 348(e.g., as shown in FIG. 4C), which may be a microcontroller, aprogrammable logic device (PLD), a microprocessor, an applicationspecific integrated circuit (ASIC), a field-programmable gate array(FPGA), or any other suitable processing device. The digital processingdevice 348 may be a part of the voltage sense circuit 344 or astand-alone device (e.g., as shown in FIG. 4C) comprised within thecalibration device (e.g., the calibration device 340) and havinginterface(s) to either or both of the voltage sensing circuit and thecommunication circuit. The various components of the calibration device(e.g., the calibration device 300, 320, or 340) may be powered by a samepower supply (e.g., the power supply 309, 329, or 349). Alternatively,separate power supplies may be provided for one or more components ofthe calibration device.

FIG. 5 is a simplified flowchart of an example calibration procedure 400that may be executed by a control circuit of a load regulation device(e.g., a control circuit of the load regulation device 110 of FIG. 1and/or the control circuit 220 of the load regulation device 200 of FIG.3). For example, the calibration procedure 400 may be executed when theload regulation device is powered up at step 410. The calibrationprocedure 400 may also be executed in response to the actuation of abutton of the load regulation device and/or in response to a digitalmessage received by the load regulation device at step 410. The controlcircuit may first adjust the magnitude of the output voltage V_(OUT) ofthe load regulation device to an initial output voltage V_(INIT) (e.g.,at approximately the rated voltage V_(RATED) of an electrical load) atstep 412. The control circuit may then wait to receive feedback (e.g., adigital message or a current spike indicating whether the load voltageV_(LOAD) has exceeded a predetermined level) at step 414 until a timeout(e.g., approximately one second) expires at step 416.

If the control circuit has not received feedback at step 414 when thetimeout expires at step 416, the control circuit may then determine ifthe magnitude of the output voltage V_(OUT) has reached a maximum outputvoltage V_(MAX), which may be, for example, approximately 20% greaterthan the rated voltage V_(RATED) of the electrical load (e.g.,V_(MAX)=1.2·V_(RATED)) at step 418. If the magnitude of the outputvoltage has not exceeded the maximum output voltage V_(MAX) at step 418,the control circuit may increase the magnitude of the output voltageV_(OUT) by a voltage step A_(OUT) (e.g., approximately 0.2 volt) at step420, before the control circuit once again waits to see if feedback hasbeen received at steps 414 and 416. When the control circuit receivesfeedback (e.g., that the load voltage V_(LOAD) has exceeded thepredetermined level) at step 414, the control circuit may decrease theoutput voltage V_(OUT) slightly (e.g., by the voltage step A_(OUT) atstep 422) and store the final value of the output voltage V_(OUT) inmemory at step 424, before the calibration procedure 400 exits. When thecontrol circuit determines that the magnitude of the output voltageV_(OUT) has reached the maximum output voltage V_(MAX) at step 418, thecontrol circuit may adjust the magnitude of the output voltage V_(OUT)to a default voltage (e.g., approximately equal to the rated voltage) atstep 426 and the calibration procedure 400 exits.

In lieu of gradually adjusting the output voltage V_(OUT) (e.g., througha plurality of period steps A_(OUT)) until receiving feedback indicatingthat the load voltage V_(LOAD) has reached or exceeded a predeterminedlevel, the control circuit may be configured to apply (e.g., all atonce) a specific amount of adjustment to the magnitude of the outputvoltage V_(OUT) based on information contained in the feedback (e.g., adigital message indicating the discrepancy between the load voltageV_(LOAD) and the predetermined level). FIG. 6 illustrates such anexample calibration procedure 500. For example, the calibrationprocedure 500 may be executed when the load regulation device is poweredup at step 510. The calibration procedure 500 may also be executed inresponse to the actuation of a button of the load regulation deviceand/or in response to a digital message received by the load regulationdevice at step 510. The control circuit may first adjust the magnitudeof the output voltage V_(OUT) of the load regulation device to aninitial output voltage V_(INIT) (e.g., at approximately the ratedvoltage V_(RATED) of an electrical load) at step 512. The controlcircuit may then wait to receive feedback at step 514 until a timeout(e.g., approximately one second) expires at step 516. The feedback maycomprise a digital message indicating the magnitude of the load voltageV_(LOAD) and/or the discrepancy between the load voltage V_(LOAD) andthe predetermined level. The control circuit may be configured to usethe feedback information to determine and apply, at step 520, anadjustment (e.g., an increase, a decrease, or no adjustment) to theoutput voltage V_(OUT) such that the load voltage V_(LOAD) may reachapproximately the predetermined level. The maximum amount of adjustmentmay be capped at a certain level to ensure that the output voltageV_(OUT) does not exceed a maximum output voltage V_(MAX), which may be,for example, approximately 20% greater than the rated voltage V_(RATED)of the electrical load (e.g., V_(MAX)=1.2·V_(RATED)). If, at step 514,the control circuit does not receive any feedback when the timeoutexpires at step 516, the control circuit may adjust the magnitude of theoutput voltage V_(OUT) to a default voltage (e.g., approximately equalto the rated voltage) at step 518 and the calibration procedure 500exits.

FIG. 7 is a simplified flowchart of an example feedback procedure 600executed by a control circuit of a calibration device (e.g., a controlcircuit of the calibration device 130 shown in FIG. 1 and/or the digitalcontroller of the calibration devices 300, 320, 340 shown in FIGS.4A-4C) while calibrating a load voltage V_(LOAD) across an electricalload (e.g., an LED light source). For example, the feedback procedure600 may be executed periodically (e.g., once a day) at step 610. Theperiod at which the feedback procedure 600 is executed may be configuredby a user. At step 612, the control circuit may sample a scaled voltagehaving a magnitude that is proportional to the magnitude of the loadvoltage V_(LOAD) across the electrical load (e.g., an LED light source).If the magnitude of the scaled voltage V_(SCALED) is greater than orequal to a threshold voltage V_(TH) indicating that the magnitude of theload voltage has reached or exceeded a predetermined voltage (e.g., therated voltage of the LED light source) at step 614, the control circuitmay provide feedback (e.g., via a digital message or a current spike) atstep 616, before the feedback procedure 600 exits. If the magnitude ofthe scaled voltage V_(SCALED) is less than the threshold voltage V_(TH)at step 614, the feedback procedure 600 simply exits without feedbackbeing provided.

In lieu of comparing V_(SCALED) to V_(TH), and determining whether themagnitude of the load voltage has reached or exceeded the predeterminedvoltage at step 614, the control circuit may be configured to determinethe actual magnitude of the load voltage V_(LOAD) and/or the discrepancybetween the load voltage V_(LOAD) and the predetermined level at step614. The control circuit may then provide feedback (e.g., via a digitalmessage) at step 616 concerning the actual magnitude of the loadvoltage, before the feedback procedure 600 exits.

FIG. 8 is a simplified block diagram of an example load control system700 having a multiple-output load regulation device 710 (e.g., an LEDdriver) for controlling the amount of power delivered to a plurality ofelectrical loads 702A, 702B, 702C (e.g., LED light sources). Themultiple-output load regulation device 710 may be coupled to a powersource, e.g., an AC power source 704 (as shown in FIG. 8) or a DC powersource. The electrical loads 702A, 702B, 702C may each be characterizedby a respective rated load voltage (e.g., approximately 24 volts for anLED light source). The multiple-output load regulation device 710 maygenerate multiple output voltages V_(OUT1), V_(OUT2), V_(OUT3), whichmay be coupled to the respective electrical loads 702A, 702B, 702C viarespective runs of load wiring 706A, 706B, 706C. To generate themultiple output voltages V_(OUT1), V_(OUT2), V_(OUT3), themultiple-output load regulation device 710 may comprise multiple loadregulation circuits (not shown), e.g., each similar to the loadregulation circuit 210 of the load regulation device 200 of FIG. 3.

Each electrical load 702A, 702B, 702C may develop a respective loadvoltage V_(LOAD1), V_(LOAD2), V_(LOAD3), and may conduct a respectiveload current I_(LOAD1), I_(LOAD2), I_(LOAD3). Where the electrical loads702A, 702B, 702C comprise LED light sources, the load regulation device710 may be configured to individually turn each of the LED light sourceson and off. The multiple-output load regulation device 710 may befurther configured to individually adjust the intensity of each of theLED light sources between a minimum intensity (e.g., approximately 1%)and a maximum intensity (e.g., approximately 100%). The load regulationdevice 710 may be configured to pulse-width modulate or pulse-frequencymodulate each of the output voltages V_(OUT1), V_(OUT2), V_(OUT3) toadjust the intensity of the respective LED light source between theminimum and maximum intensities, e.g., by adjusting the duty cycle orfrequency of the output voltage, respectively. The load regulationdevice 710 may be configured to receive wireless signals (e.g., RFsignals) from one or more input devices (not shown) as described herein,and to control the electrical loads 702A, 702B, 702C in response to thereceived wireless signals.

Because the lengths of the respective runs of load wiring 706A, 706B,706C between the multiple-output load regulation device 710 and therespective electrical loads 702A, 702B, 702C may be different, themagnitudes of the respective load voltages V_(LOAD1), V_(LOAD2),V_(LOAD3) at the electrical loads 702A, 702B, 702C may be different andmay differ from the magnitudes of the respective output voltagesV_(OUT1), V_(OUT2), V_(OUT3) at the load regulation device 710. Themultiple-output load regulation device 710 may be configured to executea calibration procedure (e.g., the calibration procedure 400 or 500shown in FIGS. 5-6) for one or more of the output voltages V_(OUT1),V_(OUT2), V_(OUT3). If the electrical loads 702A, 702B, 702C all havethe same rated voltage, the multiple-output load regulation device 710may be configured to automatically calibrate the magnitude of one ormore of the output voltages V_(OUT1), V_(OUT2), V_(OUT3), such that themagnitudes of the load voltages V_(LOAD1), V_(LOAD2), V_(LOAD3) may allbe approximately equal to the rated voltage of the electrical loads. Ifthe electrical loads 702A, 702B, 702C have different rated voltages, themultiple-output load regulation device 710 may be configured toautomatically calibrate the magnitude of one or more of the outputvoltages V_(OUT1), V_(OUT2), V_(OUT3) such that the magnitudes of theload voltages V_(LOAD1), V_(LOAD2), V_(LOAD3) may be approximately equalto the respective rated voltage.

The load control system 700 may comprise multiple calibration devices730A, 730B, 730C coupled to (e.g., in parallel with) the respectiveelectrical loads 702A, 702B, 702C near (e.g., immediately adjacent to)the electrical loads. The exact distance between each calibration deviceand the corresponding electrical load may vary from one installation tothe next, but it is contemplated that the calibration device should beplaced at a location that enables the calibration device to fairlyaccurately measure and/or control one or more operating parameters ofthe electrical load (e.g., without significant impact from the loadwiring). In some examples, the calibration devices 730A, 730B, 730C mayeach be located at (e.g., being a part of) the electrical load. Forinstance, the electrical load may comprise an enclosure and thecalibration device (e.g., a calibration circuit) may be installed insidethe enclosure to measure and/or control one or more operating parametersof the electrical load. The calibration devices 730A, 730B, 730C mayeach be similar to the calibration devices 300, 320, 340 shown in FIGS.4A-4C. The calibration devices 730A, 730B, 730C may each be configuredto sense the magnitude of the respective load voltage V_(LOAD1),V_(LOAD2), V_(LOAD3) across the adjacent electrical load 702A, 702B,702C and provide feedback to the load regulation device 710 in responseto sensing magnitude of the load voltage. For example, during thecalibration procedure, the multiple-output load regulation device 710may be configured to gradually increase (e.g., step up) the magnitude ofeach of the output voltages V_(OUT1), V_(OUT2), V_(OUT3) until the loadregulation device 710 receives the feedback from the respectivecalibration device 730A, 730B, 730C that the respective load voltageV_(LOAD1), V_(LOAD2), V_(LOAD3) has exceeded the predetermined level.For example, the calibration devices 730A, 730B, 730C may be configuredto provide the feedback to the load regulation device 710 when themagnitude of the respective load voltage V_(LOAD1), V_(LOAD2), V_(LOAD3)exceeds a predetermined level (e.g., the rated load voltage). Afterreceiving the feedback from one of the calibration devices 730A, 730B,730C that the magnitude of the respective load voltage V_(LOAD1),V_(LOAD2), V_(LOAD3) has exceeded the predetermined level, the loadregulation device 710 may be configured to decrease (e.g., step down)the magnitude of the respective output voltage V_(OUT1), V_(OUT2),V_(OUT3) slightly (e.g., such that the magnitude of the load voltage nolonger exceeds the predetermined level).

In addition to or in lieu of providing feedback that the respective loadvoltage V_(LOAD1), V_(LOAD2), V_(LOAD3) has reached the predeterminedlevel, the calibration devices 730A, 730B, 730C may be configured toprovide information to the load regulation device 710 regarding theactual magnitude of the load voltage V_(LOAD1), V_(LOAD2), V_(LOAD3)and/or the discrepancy between the load voltage V_(LOAD1), V_(LOAD2),V_(LOAD3) and the predetermined level. The load regulation device 710may be configured to interpret the information provided and to adjustthe magnitude of the respective output voltage V_(OUT1), V_(OUT2),V_(OUT3) in accordance with the information such that the load voltageV_(LOAD1), V_(LOAD2), V_(LOAD3) may be approximately equal to thepredetermined level.

The load regulation device 710 may be configured to store the finalvalue of one or more of the output voltages V_(OUT1), V_(OUT2), V_(OUT3)in memory for use during normal operation. As a result of executing thecalibration procedures, the multiple-output load regulation device 710may control the output voltages V_(OUT1), V_(OUT2), V_(OUT3) todifferent magnitudes.

The calibration devices 730A, 730B, 730C may be configured to providethe feedback in different ways. For example, the calibration devices730A, 730B, 730C may be configured to send the feedback to themultiple-output load regulation device 710 by wirelessly transmittingthe feedback via wireless signals (e.g., RF signals, infrared signals,or optical signals). In addition, the calibration devices 730A, 730B,730C may be configured to transmit the feedback to the load regulationdevice 710 via the respective runs of load wiring 706A, 706B, 706C,e.g., by generating one or more current spikes (e.g., current pulses) onthe load wiring or by transmitting a digital message using a power-linecommunication (PLC) technology. Further, the load regulation device 710may be configured to receive the feedback in response to a wirelesssignal received from one or more input devices (e.g., one or moredaylight sensors where the electrical loads include LED light sources).The load regulation device 710 may also be configured to measure themagnitudes of one or more of the output voltages V_(OUT1), V_(OUT2),V_(OUT3) and the load currents I_(LOAD1), I_(LOAD2), I_(LOAD3) todetermine a relationship between the respective output voltage and therespective load current (e.g., an I-V curve), and may use therelationship to determine the magnitude of respective output voltage atwhich the magnitude of the respective load voltage V_(LOAD1), V_(LOAD2),V_(LOAD3) is approximately equal to the rated load voltage.

The multiple-output load regulation device 710 and/or the calibrationdevices 730A, 730B, 730C may be configured to initialize the calibrationprocedure for each of the output voltages V_(OUT1), V_(OUT2), V_(OUT3)in a similar manner as the load regulation device 110 and thecalibration device 130 initialize the calibration of the load controlsystem 100 of FIG. 1.

What is claimed is:
 1. A system to control power delivery to an electricload device, the system comprising: calibration device circuitrydisposed at the electric load device, the calibration device circuitryincluding: sense circuitry to measure, at a first periodic interval, aload voltage at the electric load device; and calibration device controlcircuitry communicatively coupled to the sense circuitry, thecalibration device control circuitry to: determine whether the measuredload voltage is less than a stored threshold voltage value; andresponsive to a determination that the measured load voltage is lessthan the stored threshold voltage value, generate a load voltage outputsignal at a second periodic interval; power supply circuitry to providea source voltage output, the power supply circuitry including: loadregulation circuitry to adjust the source voltage provided by the powersupply circuitry; and system control circuitry communicatively coupledto the calibration device circuitry and to the power supply circuitry,the system control circuitry to: responsive to receipt of the loadvoltage output signal at the second periodic interval, generate at athird periodic interval, a source voltage control signal, the sourcevoltage control signal to cause an incremental change, at the thirdperiodic interval, in the source voltage; and responsive to a failure toreceive the load voltage output signal at the second periodic interval,cease generation of the source voltage control signal.
 2. The system ofclaim 1 wherein the first periodic interval and the second periodicinterval are equal.
 3. The system of claim 1 wherein the second periodicinterval is shorter in duration than the third periodic interval.
 4. Thesystem of claim 1 wherein the load voltage output signal comprises acurrent spike on power wiring delivering the output voltage to theelectric load device.
 5. The system of claim 1: wherein the calibrationdevice further comprises wireless communication interface circuitry; andwherein the load voltage output signal comprises a wireless signalcommunicated to the system control circuitry.
 6. The system of claim 1:wherein the calibration device further comprises power linecommunication interface circuitry; and wherein the load voltage outputsignal comprises a signal communicated to the system control circuitryvia power wiring conductively coupling the power supply circuitry to theelectric load device.
 7. The system of claim 1, wherein the load voltageoutput signal includes data representative of the voltage measured bythe sense circuitry at the electric load device.
 8. The system of claim7, the system control circuitry to further: develop a relationshipbetween the source output voltage and the load voltage using thereceived data representative of the voltage measured by the sensecircuitry at the electric load device.
 9. The system of claim 8 thecontrol circuitry to further: responsive to receipt of an input thatincludes data representative of a target load voltage, determine asource voltage to deliver the target load voltage at the electric loaddevice using the source voltage/load voltage relationship; and cause thepower supply circuitry to provide a voltage output at the determinedsource voltage.
 10. A system to control power delivery to an electricload device, the system comprising: calibration device circuitrydisposed at the electric load device, the calibration device circuitryincluding: voltage sense circuitry to measure, at a first periodicinterval, a load voltage at the electric load device; and calibrationdevice control circuitry communicatively coupled to the voltage sensecircuitry, the calibration device control circuitry to: determine, at asecond periodic interval, whether the measured load voltage exceeds astored threshold voltage value; and responsive to a determination thatthe measured load voltage exceeds the stored threshold voltage value,generate a load voltage output signal; power supply circuitry to providea source voltage, the power supply circuitry including: load regulationcircuitry to adjust the source voltage provided by the power supplycircuitry; and system control circuitry communicatively coupled to thecalibration device circuitry and to the power supply circuitry, thesystem control circuitry to: responsive to an absence of the loadvoltage output signal, generate at a third periodic interval, a sourcevoltage control signal to cause an incremental change in the sourcevoltage at the third periodic interval; and responsive to receipt of theload voltage output signal cease generation of the source voltagecontrol signal.
 11. The system of claim 10 wherein the first periodicinterval and the second periodic interval are equal.
 12. The system ofclaim 11 wherein the second periodic interval is shorter in durationthan the third periodic interval.
 13. The system of claim 10 wherein thefirst periodic interval is shorter in duration than the second periodicinterval.
 14. The system of claim 10 wherein the load voltage outputsignal comprises a current spike on power wiring delivering the outputvoltage to the electric load device.
 15. The system of claim 10: whereinthe calibration device further comprises wireless communicationinterface circuitry; and wherein the load voltage output signalcomprises a wireless signal communicated to the system controlcircuitry.
 16. The system of claim 10: wherein the calibration devicefurther comprises power line communication interface circuitry; andwherein the load voltage output signal comprises a signal communicatedto the system control circuitry via power wiring conductively couplingthe power supply circuitry to the electric load device.